@GwtCompatible public abstract class IteratorTester<E> extends Object
Iterator.next()
, Iterator.hasNext()
and Iterator.remove()
operations. This utility takes the brute-force approach of trying all
possible sequences of these operations, up to a given number of steps. So, if
the caller specifies to use n steps, a total of 3^n tests are
actually performed.
For instance, if steps is 5, one example sequence that will be tested is:
This particular order of operations may be unrealistic, and testing all 3^5 of them may be thought of as overkill; however, it's difficult to determine which proper subset of this massive set would be sufficient to expose any possible bug. Brute force is simpler.
To use this class the concrete subclass must implement the
AbstractIteratorTester.newTargetIterator()
method. This is because it's
impossible to test an Iterator without changing its state, so the tester
needs a steady supply of fresh Iterators.
If your iterator supports modification through remove()
, you may
wish to override the verify() method, which is called after
each sequence and is guaranteed to be called using the latest values
obtained from AbstractIteratorTester.newTargetIterator()
.
Modifier and Type | Class and Description |
---|---|
static class |
AbstractIteratorTester.KnownOrder |
Modifier | Constructor and Description |
---|---|
protected |
IteratorTester(int steps,
Iterable<? extends IteratorFeature> features,
Iterable<E> expectedElements,
AbstractIteratorTester.KnownOrder knownOrder)
Creates an IteratorTester.
|
Modifier and Type | Method and Description |
---|---|
protected Iterable<com.google.common.collect.testing.AbstractIteratorTester.Stimulus<E,Iterator<E>>> |
getStimulusValues()
I'd like to make this a parameter to the constructor, but I can't because
the stimulus instances refer to
this . |
protected abstract I |
newTargetIterator()
Returns a new target iterator each time it's called.
|
void |
test()
Executes the test.
|
protected void |
verify(List<E> elements)
Override this to verify anything after running a list of Stimuli.
|
protected IteratorTester(int steps, Iterable<? extends IteratorFeature> features, Iterable<E> expectedElements, AbstractIteratorTester.KnownOrder knownOrder)
steps
- how many operations to test for each tested pair of iteratorsfeatures
- the features supported by the iteratorprotected final Iterable<com.google.common.collect.testing.AbstractIteratorTester.Stimulus<E,Iterator<E>>> getStimulusValues()
this
.protected abstract I newTargetIterator()
protected void verify(List<E> elements)
For example, verify that calls to remove() actually removed the correct elements.
elements
- the expected elements passed to the constructor, as mutated
by remove()
, set()
, and add()
callspublic final void test()
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